The present invention relates to a keyboard switch apparatus for an electronic musical instrument and, more particularly, to a keyboard switch apparatus for an electronic musical instrument in which upon depression of a key two switches are closed at different timings according to the key depression speed or force so that by detecting the time difference between the timings the volume, envelope and/or tone color of a musical tone can be controlled, which is often called as touch response control.
Various types of conventional keyboard switch apparatuses of this type to be used in electronic musical instruments have been proposed. These conventional keyboard switch apparatuses have both advantages and disadvantages and can be exemplified by a switch apparatus having a dome-like flexible member made of rubber or the like and a movable contact formed therein, as described in Japanese Patent Prepublication Nos. 53-116141 and 59-142600.
In a conventional keyboard switch apparatus with the structure described above, the flexible member is manufactured by injection molding. Mold preparation cost is high, which leads to high costs for keyboard switch apparatuses. When keyboard switch apparatuses are manufactured in mass production lines, sizes of the switch apparatuses may be different for each mold, thus presenting the problem of dimensional precision. Furthermore, it is difficult to prepare profiles with under-cut portions in such a conventional injection-molded switch structure. In this sense, the shape of the switch apparatus is limited. Since these switch apparatuses are designed as single discrete devices, they require the structure of a switch as well as the complete structure of a single discrete device.